1. Technical Field
The present invention relates to changing the ambient air temperature, cleanliness, and humidity inside a structure and, more specifically, to a cooling method and apparatus which provides a simple, yet very energy-efficient, means of cooling the interior of a structure with clean, humidified air.
2. Background
Human beings are known for their ability to adapt to their environment and to adapt their environment to them. One example of this quality is the continued expansion of human populations into areas previously deemed inhospitable to human life. Desert communities such as Phoenix, Arizona and Las Vegas, Nev. are two well-known and rapidly growing areas which support burgeoning populations. In order to survive in these hot, desert climates, most structures designed for human occupation are provided with one or more systems for cooling the air inside the structure. Some of the various types of systems used to cool the air inside a structure are typically rated by using a system which assigns a Seasonal Energy Efficiency Ratio (SEER) rating or number to the system. A higher SEER rating indicates a more efficient system when compared with a system having a lower SEER rating.
One popular method of cooling the air inside a structure that has been adopted in many hot climates is the evaporative cooler. Evaporative coolers use a simple combination of a water pump, absorbent cooling pads, and a fan to provide cool air. Using basic principles of gravity and evaporation, air is cooled by forcing it through the evaporative cooler. Water is pumped into water-retaining pads which line the interior surface of the evaporative cooler and the outside air is drawn into the evaporative cooler by a large blower fan. By drawing the outside air through the water-soaked cooling pads, heat is transferred from the air to the water as water evaporation occurs and the cooled air is blown into the structure, thereby cooling the interior of the structure. The passage of the air through the pads deposits many airborne contaminants into the water and onto the pads.
While generally effective, evaporative coolers have certain well-known limitations. For example, as the outside air temperature increases, the evaporation process cannot sufficiently lower the temperature of the air in a structure to provide an acceptable temperature for human occupation. The evaporation rate, however, will continue to increase as the temperature increases. In addition, in very humid climates, evaporative coolers can be ineffective for cooling occupied structures at even relatively low ambient air temperatures due to the high amount of water vapor in the air. Once the air is saturated with water vapor, no additional evaporative cooling can take place. However, cooling by conduction and convection can still take place, so that pad water at 80 degrees F. can still cool hotter air at 100% humidity that transits the pads. Furthermore, pad water at 90 degrees F. can still be cooled by cooler air at 100% humidity that transits the pads.
To overcome the limitations associated with evaporative coolers, people living in many desert climates have turned to refrigerated air-conditioning systems to cool the air inside a structure. Instead of using the principles of evaporation, traditional refrigerated air-conditioning systems use the properties of refrigerant gases such as Freon to cool the temperature of the air.
While very effective, refrigerated air-conditioning systems suffer from several undesirable characteristics. Foremost, these systems are relatively expensive to operate when compared to the nominal operational costs associated with most evaporative coolers. During the hottest part of the summer in more severe desert climates, the cooling costs associated with supplying electricity for a refrigerated air-conditioning system for even modest-sized homes can become exorbitant. Secondly, the compressors, fans, and motors used in typical residential air-conditioning systems are very loud and can contribute to a high level of ambient noise in some residential areas. In addition, the size and shape of the various components of the refrigerated air-conditioning system makes them somewhat unsightly next to a residence. Finally, the continued growth in the use of air-conditioning systems requires an ever-increasing expenditure of precious resources to generate the electricity necessary to operate the systems.
In some areas of the country, evaporative coolers and refrigerated air conditioning systems are both used, during different parts of the season, to cool the air inside a structure. In a typical scenario, an evaporative cooler may be used to reduce the ambient air temperature inside a structure during the relatively cooler and drier spring and early summer months (i.e., April, May, and June). Then, once the outside ambient air temperature and/or humidity has exceeded the capabilities of the evaporative cooler, typically in July, August, and possibly September, the evaporative cooler is switched off and the refrigerated air-conditioning system is used to reduce the ambient air temperature. Towards the end of the summer months as the fall season arrives, temperatures and humidity levels drop, and the evaporative cooler may once again be adequate to provide the desired cooling effect. While alternating the use of the two systems provides a better trade off between efficiency and effectiveness than using either system alone, these alternate use systems still leave room for improvement.
Some combinations of evaporative coolers and refrigerated air conditioners are currently practiced. U.S. Pat. No. 5,778,696 to Conner (Jul. 14, 1998) discloses an apparatus in which water from a swimming pool is first used to cool the condenser of a refrigerated air conditioner and is then used as input water to an evaporative cooler. An unevaporated portion of the water is returned to the swimming pool as cooled water. When the refrigerated air conditioner is running, the air output of the evaporative cooler is directed into an attic space to lessen the workload of the air conditioner by reducing the heat flow to the living spaces and adjacent spaces.
While these systems substantially improved cooling and energy efficiency, room for improvement remained. When the refrigerated air conditioner is cooling a dwelling space portion of the structure and the evaporative cooler is cooling the attic, contaminants within the dwelling space are recirculated. Contaminants are both generated within the dwelling space and enter the dwelling space from outdoors. Air filters trap large dust particles but miss small particles and gases. Because the air pressure is the same inside the dwelling space as outside the house, contaminants can migrate into the dwelling space from outdoors. As a result, the summer months may be less healthy for the occupants than the winter months. In late Spring and early Fall, the evaporative cooler blows cooled, cleaned outside air into the building, affecting a complete change in the dwelling space air several times a day. Air typically exits the house through cracks around doors and windows, as well as some vents. Furthermore, the air from an evaporative cooler is humidified as a byproduct of the evaporative cooling process. Desert air is sometimes too dry for human health and comfort, so the humidity provided by evaporative coolers is a benefit.
What is needed, therefore, is an apparatus and method for more efficiently cooling the interior of structures, particularly in hot desert climates where refrigeration is the primary method of cooling, while simultaneously decreasing the overall consumption of electric power and providing a cleaner, healthier supply of air to breath. Without developing more efficient methods for providing cool, clean air in hot desert climates, operating expenses borne by consumers for refrigerated air-conditioning systems and health care will continue to rise and our earth""s natural resources will continue to be diminished at an excessive rate.
An embodiment of the present invention utilizes a water reservoir, at least one water pump, an evaporative cooler, ductwork with controllable louvers, and a refrigerated air-conditioning system with a water-cooled condenser to provide a cleaner and more energy-efficient means (SEER values up to 24 or more, including the evaporative cooler power consumption) for cooling a house, an office, a retail store, or other enclosed space. In addition, by selectively using the evaporative cooler to cool the interior of adjacent spaces in a structure, such as an attic, garage, or workshop, the cooled adjacent spaces act as a buffer zone between sun-heated roof and exterior walls and the ceiling and walls of the structure which is to be cooled. The introduction of the cooled output air from the evaporative cooler into the adjacent space significantly reduces the temperature differential between the air inside the dwelling portion of the structure and the ambient air temperature in the adjacent space. This, in turn, reduces the cooling load on the refrigerated air-conditioning system, that is used to cool the dwelling space inside the structure. The combination of the two cooling systems, operating in tandem to control the air temperature inside the structure, provides a better trade-off between effectiveness and efficiency than either system operating independently over the whole range of outside temperature and humidity. This system will reduce the overall operating costs and energy consumption required to cool the interior space of a given structure to one-third of the cost of systems using only refrigerated air conditioners.
Additionally, since water-cooled condensers are more energy-efficient than the typical air-cooled condenser coils used in most residential and other small air-conditioning systems, the use of a water-cooled condenser in conjunction with the present invention further reduces operating costs. A refrigerated air-conditioning system utilizing an embodiment of the present invention utilizes smaller components and is less obtrusive, visually and audibly, than a more conventional cooling system.
During periods when the refrigerated air-conditioning system is the primary source of cool air to the living space, an embodiment of the invention also provides for adding a portion of the evaporative cooler output air flow with the air flow of the refrigerated air-conditioning system. Adding air flows has three benefits. The mixed air is humidified and is cleaner than air recirculated by an air conditioner alone. Because the evaporative cooler uses outdoor air, adding evaporative cooler output air to refrigerated air conditioner air increases the total amount of air going into the living space. This increase in the amount of living space air slightly pressurizes the living space, thereby reducing infiltration of contaminants from outdoors, as well as exhausting a portion of the inside contaminated air to the outside, through existing house vents such as stove, bathroom, and gas heater vents. In an embodiment, the amount of evaporative cooler output added to the refrigerated air conditioning system output is determined by a control system regulating humidity, temperature, pressure, or any combination thereof.
In an embodiment of the present invention, a water reservoir of the evaporative cooler is used to provide water for the evaporative cooler and for the water-cooled condenser as an integral part of the air-cooling system. Depending upon operating parameters, it may be desirable to include a mechanism or method for controlling the hardness of water supplied from the water storage source to the water-cooled condenser. A purge-type of mechanism that removes a portion of high-hardness water is suitable. Such a mechanism may include a conductivity sensor positioned to contact water supplied to the condenser, a hardness monitor linked to the sensor, and control valve triggered to open by the hardness monitor.